Strangely, stripping them of the World Cup would probably sting as much as any economic sanction.
However, the Russian economy is already on the verge of a depression and any reduction in foreign revenue from gas or oil sales will quite quickly push it over the brink - notice how they haven't turned off the spigots of their own accord (for their European customers).
Here's the problem, we are already dealing with a man who is committed to restoring the pride of what he sees as a humbled and defeated nation. If we push the entire country into a severe economic depression do you think that will soften them, or harden them into thinking they have nothing left to lose.
International brinksmanship is a difficult and dangerous game, especially when the other guy has an entire arsenal of nuclear weapons and hates you for what he sees as a) being the Cold War victor, and b) having an extravagant and cushy lifestyle compared to his own somewhat impoverished citizens.
As that noted international ambassador Elmer Fudd once said - "we need to be vewy, vewy careful".